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Check your List-Unsubscribe and one-click headers
Paste an email's raw headers. Get a check of List-Unsubscribe, List-Unsubscribe-Post and the DKIM signature against RFC 8058, or generate the two header lines from your unsubscribe URL. Free, no account.
What one-click unsubscribe needs
From RFC 8058, Signaling One-Click Functionality for List Email Headers (checked 5 Nov 2026): a List-Unsubscribe header with an HTTPS URL, a
List-Unsubscribe-Post header whose value is exactly List-Unsubscribe=One-Click, and a valid DKIM
signature that covers both. The mail client then sends a POST to the URL when the recipient
clicks Unsubscribe; the server must act on it without a redirect and without cookies or a login.
A mailto: address can sit next to the URL for older clients.
Google's guidelines for senders of more than 5,000 messages a day to Gmail require one-click unsubscribe for marketing mail: Google, Email sender guidelines (checked 4 Nov 2026).
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Questions
The header that marks a List-Unsubscribe URL as one-click. Its value must be exactly List-Unsubscribe=One-Click; the mail client then unsubscribes the recipient with a single POST.
Not for one-click. RFC 8058 one-click needs an HTTPS URL in List-Unsubscribe; a mailto: address can be added next to it.
Yes. RFC 8058 requires a valid DKIM signature that covers List-Unsubscribe and List-Unsubscribe-Post, so a forwarder cannot change them.
No. The headers are checked in memory for that one request and the page is not cached.
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